GLOBAL CHANGE: THE GEOLOGICAL SURVEY OF CANADA PERSPECTIVE

Geological processes are fundamental to the understanding of Global Change and the geological record provides a baseline against which to assess the nature and significance of contemporary global change (Price 1986)     

Two‐regime Pattern in Human Mobility: Evidence from GPS Taxi Trajectory Data

Research on complex systems has identified various aggregate relationships in phenomena that describe these systems. Travel length has been characterized by negative power distributions. Controversy, however, exists over whether mobility patterns can be modeled in terms of a simple power law (Lévy flight model) or that more complicated power laws (exponential power law, truncated Pareto) are required. This study concentrates on two issues: testing the validity of exponential power laws and truncated Pareto distributions in urban systems to describe aggregate mobility patterns, and examining differences in mobility patterns for different travel purposes. The article describes the results of an analysis of Global Positioning System (GPS) taxi trajectory data, collected in Guangzhou, China, to identify mobility patterns in the city. The least squares statistic is used to estimate the parameters of the distribution functions. Results suggest that a fusion of functions, based on an exponential power law and a truncated Pareto distribution, represents the travel time distribution best. Moreover, the findings of this study indicate different mobility patterns to exist for different travel purposes.     

The visibility of past trees and woodland: testing the value of insect remains

The reconstruction of woodland history is important in relation to archaeological, ecological, biogeographical and evolutionary problems, and insect remains are a significant source of relevant information. Fully natural interglacial and Holocene ‘waterlogged’ deposits assumed to have formed in woodland generally contain abundant macrofossils of both plants and insects indicative of trees. In contrast, British archaeological deposits rich in macrofossil remains of trees often lack, or contain very few, tree-associated insects. To cast light on this contradiction, assemblages of insect (Coleoptera and Hemiptera) remains from a range of modern deposits with various spatial relationships to woodland and trees have been analysed. The proportions of tree-associated insects varied greatly. There was a general trend from higher values in woodland and near to isolated trees of species supporting a rich insect fauna, to low or zero values where there were no trees. However, low values sometimes occurred in woods or near trees, so that rarity of tree-associated insects in archaeological deposits does not always carry the implication of a treeless environment. Further investigation is suggested, with emphasis on the importance of identifying isolated trees, scrub and hedges as a resource for humans and wildlife in the past.